I realize that I'm offering critique without offering suggestions and that isn't helpful.
What I'm finding is that most of my potential abilities looks great on paper but when I have them in the game they aren't useful.
Spamming sounds insanely strong but in reality once you're in the mid-levels you won't have an opportunity to seriously spam your blasts.
A lot of the utility invocations have so many drawbacks they just aren't something feasable - I noticed that at the level 3 invocations. The fire aura shoots light off - that's not helpful. The shadow aura gives 100 percent concealment: Cool. But when my friends walk up to me it saps their strength. and it only lasts 5 rounds. And it doesn't work in the light so if I get jumped on the road during daytime, my only real defensive ability is useless. The fire wall is really strong. But it's as dangerous to friendlies as foes (though with planning that can be somewhat mitigated)
I have regularly @relevel-ed each level for awhile now to test out each invocations and I'm seriously finding it hard to settle because I have to decide which one hurts me the least when I use it. (Eldritch chain though, is good. No notes)
Most warlock invocations are so niche they won't come up all the time, and I think that's the issue. I think the class needs the utility and toolbox invocations increased in usefulness in more situations. We only have 3 per level - when an invovation has such a narrow and niche use it seriously hurts our ability to impact any scene that requires a use of power.
It's just such a bummer to read all these powers that SOUND cool but when you get in-world and use them they turn out to be a waste of a valuable and rare invocation slot. We only get 3 each level. Losing one that is useless in adventuring and next-to-useless in RP is such a bummer and disappointment.